The fabrication of a semiconductor device involves a plurality of discrete and complex processes. The semiconductor substrate typically undergoes many processes during the fabrication process. These processes may occur in a processing chamber, which may be maintained at a different processing condition than the environment. For example, the processing chamber may be maintained at vacuum conditions. In certain embodiments, a load lock is used to separate the processing chamber from the external environment. One or more substrate handling robots are disposed in the processing chamber and move the substrate from the load lock to the platen on which the substrate is disposed during processing.
The processing chamber may also include an alignment station which aligns the substrate in the proper orientation. The substrate is removed from the load lock and placed on the alignment station by the substrate handling robot. This alignment station then rotates the substrate so that the notch, or index mark, on the substrate is disposed in a known position. In this way, the substrates are aligned in a known orientation prior to processing. After the orientation is completed, the substrate handling robot removes the substrate from the alignment station and places the substrate on the platen for processing.
Heating substrates before and/or after processing is common in many semiconductor fabrication processes. In many cases, the substrate is heated to a temperature close to the process temperature and then transported to the platen. This preheating may help prevent substrate warping, popping and movement when the cold substrate contacts the hot platen. These phenomenon may cause the creation of particles and mishandling, and may reduce overall process yield.
Additionally, in some embodiments, a substrate may be warmed after being subjected to a cold process to eliminate the possibility of condensation when the substrate exits the processing chamber.
In certain embodiments, a dedicated preheating station may be used to perform this function. The preheating station may comprise one or more infrared lamps that are focused on the substrate. While the preheating station is effective at raising the temperature of the substrate, the preheating station has a negative impact on throughput. Specifically, a substrate may be disposed at the preheating station for a significant amount of time in order for the substrate to reach the desired temperature.
In those embodiments using a preheating station, typically, after alignment, the substrate may be moved by the substrate handling robot to a preheating station, which warms the substrate. When the substrate has reached the target temperature, the substrate handling robot transfers the substrate from the preheating station to the platen.
However, this preheating station, while effective in heating the substrate, is time consuming. Further, the preheating station has to be within the reach of the substrate handling robot and therefore, the area near the load lock may become very congested, making maintenance and repair extremely different. Further, in certain embodiments, multiple load locks with multiple substrate handling robots are used. In these embodiments, there may also be multiple preheating stations, where each is associated with a respective substrate handling robot. The addition of preheating stations adds complexity and cost to the overall system. Further, these preheating stations also increase the overall size of the processing chamber.
It would be beneficial if there were an apparatus to heat the substrates without the use of a dedicated preheating station. As stated above, these preheating stations consume valuable space and also add processing time to each substrate, reducing throughput. Further, it would be beneficial if this heating could be accomplished without adding additional processing time or stations to the fabrication process. It would be advantageous if the substrate could be heated while being oriented on the alignment station. In this way, the time used to orient the substrate could also be used to heat the substrate, which reduces the time dedicated to heating the substrate and increasing throughput.